This is very weird.
The only problem I see here is the 19VAC at the B+ terminal of the rectifier. It should not be over 2 or 3 VAC.
As you are obviously aware, there are only 2 components in the charging system - the stator and the regulator.
The stator produces an AC output, approximately 40-60VAC @ 3600 rpm, which goes to the regulator.
The regulator is a set of diodes that convert the AC input to DC output, approximately 13.6 - 14.7 VDC @ 3600 rpm.
The fact that you are reading -24VDC makes me wonder 2 things.
I am certainly not trying to imply anything here - I am just keeping an open mind in attempting to help you get to the bottom of this.
1. Since you are getting a negative voltage reading, are your meter leads connected to the proper terminals of your meter?
2. With a consistent 24V reading, is it possible that your meter is set to the incorrect scale, or possibly bad? Have you calibrated/tested your meter against a known power source?